Missing Admin Account in OSX El Capitan
A couple of years ago someone reached out to me saying her main user account had disappeared. At the time the fix was pretty simple: using the terminal to re-run setup assistant, punching in the info for the missing account exactly, and presto! Everything shows back up. Well she reached out to me today saying the same problem had happened again. She had hired another tech who'd come out and simply moved her user files to the desktop, but her user still wasn't showing up as something she could log in to. So I walked her through doing the setup assistant thing again. She restarted and her user showed up. However when she logged in she was greeted with "OSX needs to repair your library to run applications" with a password prompt. However no passwords worked. So we rebooted to recovery mode, resetpassword in Terminal, and this time it came back with "Unapproved caller. Securityagent may only be invoked by Apple Software." At this point I feel like I'm in over my head. What's the easiest way to get her back in to her user?
Sounds to me like some operating system files have been modified in a way that causes signature/checksum checking to fail. At a guess I’d think that an OS reinstall might help?